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IV.A.5. Compare Barriers to Internal Rotation for CH3CHO (Acetaldehyde)

Experimental barrier to internal rotation is 4.9+- 0.1 kJ/mol
Energy Differences (Calculated - Experimental) in kJ/mol
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Methods with predefined basis sets
semi-empirical AM1 -3.2
PM3 -2.4
molecular mechanics DREIDING 2.7

Methods with standard basis sets
3-21G 6-31G* 6-31+G** cc-pVDZ cc-pVTZ
hartree fock HF -0.1 -0.6 -0.5 1.1 -0.6
density functional B3LYP 0.5 -0.2 -0.6   0.1
wB97X-D   -0.8     -0.2
3-21G 6-31G* 6-31+G** cc-pVDZ cc-pVTZ
Moller Plesset perturbation MP2 0.5 -0.8 -1.1   0.2
Coupled Cluster CCSD   -0.9     0.0
3-21G 6-31G* 6-31+G** cc-pVDZ cc-pVTZ
For descriptions of the methods (AM1, HF, MP2, ...) and basis sets (3-21G, 3-21G*, 6-31G, ...) see the glossary in section I.C. Predefined means the basis set used is determined by the method.

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